This invention relates to an automated gear selection apparatus.
In this specification, the invention will be described with reference to gearboxes having a linear gear shifting mechanism as are commonly found in marine craft for example. Such gearboxes have a gear selector that moves linearly to select between two or more gears, such as a forward gear, a neutral gear and a reverse gear.
Linear gearboxes are typically operated by means of a manually operable lever or xe2x80x9cgearstickxe2x80x9d that is usually coupled to the gearbox""s shifting mechanism by means of a gear selector cable. In use, the lever is pushed forward to engage the forward gear, drawn into an intermediate position to engage the neutral gear and drawn fully backwards to engage a reverse gear. There are a number of disadvantages with such an arrangement.
A first disadvantage is that considerable strength may be required to operate the lever. Consequently, gear changing may be awkward or clumsy, particularly for those who are unfamiliar with controlling marine craft or do not have muscular strength.
A second disadvantage is that accidental shifting of the lever may have disastrous consequences. For example, inadvertently falling on or striking the gearstick will cause the craft to accelerate or decelerate in an uncontrolled and hazardous manner. Alternatively, in a recreational marine craft, a child may pull or push on the lever. Those who have had experience with boating will realize that such an event can be particularly dangerous. At present mechanical lockout mechanisms are known for preventing the inadvertent operation of the gearstick. However, mechanical lockout mechanisms are typically inconvenient and time-consuming to use.
It is an object of the present invention to provide a convenient and easy to use mechanism for operating a linear gear selector and to address the disadvantages described above.
According to the present invention there is provided an automated gear selection apparatus for a gearbox of a drive unit, the gearbox having a linear gear selector that is displaceable between at least a first position and a second position, the gear selection apparatus including:
an actuator including an actuator member displaceable between at least two predetermined positions corresponding to the positions of the linear gear selector;
a control means in communication with the actuator to control displacement of the actuator member, the actuator member being connectable to the gear selector for displacing said selector between at least the first and second positions; and
a user interface means operatively connected to the control means so that a user can selectively cause operation of the actuator and thus the gear selector.
A cable securing assembly may be attached to the actuator member for engaging a gear selector cable. Preferably the actuator member comprises a shaft that is extendible and retractable relative to a housing of the actuator. Alternatively the member may comprise a rotatable reel about which the gear selection cable may be wound.
The cable securing assembly may be attached to the shaft by means of a quick release member. The cable securing assembly preferably includes a handle for manual gear selection.
In a preferred embodiment the control means is configured to monitor user selection of a desired gear and in response bring the shaft to a position for selection of the desired gear. Furthermore, it is desirable that the control means is further configured to monitor the position of the shaft.
Typically the control means includes a micro-controller which operates according to firmware including:
instructions for monitoring signals from the user interface means;
instructions for bringing the shaft towards a setpoint corresponding to a signal from the user interface means, the setpoint corresponding to selection of a gear by the linear gear selector.
The firmware may further include instructions for monitoring a feedback signal indicating position of the shaft. In a preferred embodiment the feedback signal is generated by circuitry including a potentiometer coupled to the shaft.
In a preferred embodiment the microcontroller further includes instructions for user entry of setpoints comprising actuator states corresponding to a particular gear selections.
The controller may monitor a signal indicating engine revolution rate and wherein the firmware further includes instructions for determining whether or not to bring the shaft towards a setpoint on the basis of predetermined engine revolution rates.
Preferably the firmware further includes instructions for user entry of the predetermined engine revolution rates. The signal indicating engine revolution rate will typically comprise a signal from an engine ignition system of the engine. However, particularly in relation to diesel engines, the signal indicating engine revolution rate may be generated by a magnetic sensor fixed relative to a magnet attached to a rotating member of the engine.
The instructions for bringing the shaft towards a setpoint will preferably include:
instructions for monitoring the position of the shaft;
instructions for comparing the position of the shaft to a current setpoint;
instructions for moving the shaft towards the setpoint at a speed that is dependent on the deviation of the position of the shaft from the setpoint in order to reduce overshoot.
The user interface typically comprises a console including user data input and output means.
Preferably the user interface means includes a micro-controller arranged to communicate with a micro-controller located in the control means.
The interface means may include a switch means or key that is connected to the control means to provide the control means with command signals relating to a gear selected by a user. The switch means may include a console that is readily accessible by a user. The console may incorporate a number of momentary press switches or keys. Each key may correspond with one respective predetermined position of the gear selector. A discernible signal means may be provided in the control means. The discernible signal means may be in the form of a number of LED""s (light emitting diodes) that correspond with respective gears. The LED""s may be connected to the micro-controller to indicate to a user whether or not a particular gear has been selected.
According to a further aspect of the present invention there is provided an automated gear selection apparatus for a gearbox of a drive unit, the gearbox having a linear gear selector displaceable between at least a first position and a second position, said gear selection apparatus including:
an actuator means for displacing the linear gear selector between the at least a first position a second position;
cable securing means releasably attached to the actuator means for securing a gear selector cable and including a handle for manual operation;
control means in communication with the actuator means for controlling the actuator means; and
user interface means in communication with the control means for receiving gear selections from a user.
According to a final aspect of the present invention there is provided an automated gear selection apparatus for a gearbox of a drive unit, the gearbox having a linear gear selector displaceable between at least a first position and a second position, said gear selection apparatus including:
a linear actuator including a movable shaft displaceable between at least two predetermined positions corresponding to at least the first position and the second position of the linear gear selector;
a controller coupled to the actuator to control displacement of the shaft;
a cable securing assembly attached to an end of the shaft by means of a quick release member;
a user interface connected to the controller for user selection of a position of the linear gear selector.
The invention is now described, by way of example, with reference to the accompanying drawings. The following description is for the purpose of illustrating an embodiment of the invention to a person of ordinary skill in the field. As such, the specific nature of the following description is not to be construed as limiting the scope of the invention described in the appended claims.